Constant web tension unwinding mechanism



Feb. 12, 1957 Filed March 25, 1953 R. LE B. BOWEN, JR

CONSTANT WEB TENSION UNWINDING MECHANISM 2 Sheets-Sheet l R Q g \xINVENTOR.

@ B:- Richurd'LeBoron Bowen,Jr.

KN BY & K1 3%3 Mflm \0 N ATTORNEY 1957' R. LE B. BOWEN, JR

CONSTANT WEB TENSION uuwmomc MECHANISM 2 Sheets-Sheet 2 Filed March 25,1953 JNVENTOR. Richard LeBoron Bowen, Jr.

ATTORN EY CONSTANT WEB TENSION UNWINDING MECHANISM Richard LeB. Bowen,Jr., Pawtucket, R. 3.

Application March 25, 1953, Serial No. 344,520

9 Claims. (Cl. 242-75) This invention relates to a constant web tensionunwinding mechanism and more particularly to a mechanism for maintaininga constant speed on the web unwinding mecham'sm through a variable speedtransmission responsive to the change in brake speed which reacts tocontrol the pressure on the brake.

One of the objects of the present invention is to provide a constantbraking force in a web unwinding mechanism.

Another object of the present invention is to provide a braking forcemechanism which inherently will permit the accurate duplication of thebraking force.

Other objects of the present invention will be pointed cutin part andbecome apparent in part in the following specification and claims.

The present application is related in the mental concept of web controlas expressed in my co-pending applications Serial No. 313,889, filedOctober 9, 1952, now Patent No. 2,758,472, dated August 14, 1956, andSerial No. 327,003, filed December 19, 1952.

Uniform or constant tension is a prerequisite to uniformity of productin many web processing machines such as textiles, paper, imitationleather, printing and the like. Especially is this true in coatingmachinery where the tension on the web effects the nature of theapplication of the coating being applied to the cloth. Thus, when asupply roll of cloth is placed in a machine the cloth should be drawn edat a constant speed and at a given tension so that as the diameter ofthe supply roll decreases the speed or linear travel of the cloth ismaintained constant. However, the tension on the cloth increases as thedrag on the supply roll increases because the decreasing diameterproduces more revolutions per minute. It is necessary, therefore, todecrease the drag or friction on the supply roll shaft if the tension onthe cloth is to be maintained constant. Past devices have failed toautomatically control the drag and thereby regulate the tensionaccurately in accordance with the changing tension produced as thesupply roll decreases in diameter.

This failure was due in part to the nature of the braking mechanismwhich consisted of the conventional mechanical arrangement of a brakedrum and a shoe provided with a brake lining. The coefiicient offriction between the drum and shoe varied due to the heating caused bythe period of operation and the unevenness of the parts and oil, dustaccumulation so that the brake slipped and grabbed. There was no way ofdetermining a brake setting for future use. The present inventioncontemplates an oil pump the pressure of which is always determinableand which will minimize the disadvantages of a brake drum and shoe.

Referring to the drawings in which similar characters of referenceindicate coresponding parts in all the figures:

Figure 1 shows an embodiment of the present invention in diagrammaticform, for the sake of clarity and simplicity and presents the mechanismas applied to an unwinding device. 7.

2,781,178 Patented Feb. 12, 19 57 ice Figure 2 is a diagrammatic form ofmechanism which is another modification of the mechanism illustrated inFigure 1.

Referring to the drawings and particularly to Figure 1, wherein a stripor web of material 11 is being withdrawn from a beam 12 by means of adrum 16. Beam 12 is secured to an axle 13 which has fixed to it bevelgear 14 which meshes with bevel gear 15 fixed to 'a shaft 20 of acontinuously variable speed transmission, generally indicated byreference character 17. A second shaft 21 of variable speed transmission17 is operatively connected to a gear pump generally indicated byreference character through a shaft 36, sprocket 33 fixed to shaft 36,sprocket 32 fixed to shaft 21 and chain 34 con-' necting sprockets 32,33. A reservoir 38 is provided and is operatively connected to gear pump35 through suction line 37 and discharge line 40. A discharge valve 41inserted in line controls the power exerted by the gear pump 35. Apressure gage 42 inserted in line 40 gives a relative indication of thispower.

The variable speed transmission 17 comprises a pair of parallel shafts20 and 21 rotatably mounted in a housing 22. Each shaft 20, '21 carriesa pair of coned disks 23, 24, respectively, forming expansive V pulleyswhich are splined to said shafts. Coned disks 23, 24 are opera- 7 tivelyconnected through edge-active belt 25 and may be simultaneously andoppositely adjusted to provide variable speed by the simultaneousadjustment of levers 26 and 27 which are operatively connected to coneddisk 23, 24 and pivotally separated by lever 28. The ends of levers 26,27 are fixed to threaded shaft 36 by means of threaded bearings 31, 32.The rotation of threaded shaft 30 simultaneously and oppositely movesdisks 23, 24 on shafts 20, 21, thereby varying the speed of rotation-ofshaft 20 relative to shaft 21.

Threaded shaft 39 is operatively connected to a reversible electricmotor 44 by means of sprocket 47 forming part of a slip clutch 29mounted on shaft 30, sprocket 46 fixed to motor shaft and chain 48connecting sprockets 46,47.

The discharge line 40 is in communication with a pressure switch, as forexample, a Bourdon tube 52 which controls the operation of motor 44through a switch 43. Current is supplied to motor 44 through wires and51. A switch 53 is used for reversing motor 44. It has one single polenormally closed circuit and one single pole normally open circuit. Inoperation when a roll of material is being unwound the normally closedcircuit of switch 53 connects wire 54 with the contact of switch 43.Thus when switch 43 is closed by the action of Web 11, current flowsthrough line 50, and through line 51, switch 43, switch 53, line 54, tomotor 44. The reversing action of the switch 53 will be explained later.In this initial arangement of switch 53, wire 55 is open.

In operation, web 11is being withdrawn from beam 12 by drum 16, which isdriven at a constant speed by means,

not shown, and thus withdraws Web 11 at a constant" As beam 12 isunwound, its-diameter" decreases and its speed of rotation increases.This increase in speed is transmitted to pump 35 through bevel linearvelocity.

gears 14, 15, shaft 20, cones 23, belt 25, cones 24, shaft 21, sprockets32, 33, chain 34 and shaft 36.

As soon as the pump receives the increase in'speed, the

-17, and thus is a'modification of Figure 1.

web.

When the beam 12 is completely unwound, the variable speed transmission17 has shifted to one limit in that threaded bearings 31, 32 onthreadedlshaft, 30 are'atjthe approximate minimum distance from eachother. For a fresh beam the transmission should. be. at" the oppositelimit with the bearings 32., 32at the approximate maximum distance fromeachcther. To eifect'this, hand wheel 56 fixed to shaft 21 is turned andreversing switch 53 is manually actuated, breaking contact in wire 54and making contact 'in wire 55, thereby running the motor in theopposite direction frorn'that stated above and setting-the transmissionat the. opposite limit. After the transmission has been reset,'the newbeam may be put in. It is necessary to-turn thehandwheel -56 to resetthe transmission, since the relative distances of the coned disks cannotbe changed unless the belt 25. is in motion.

threaded shaftfiii remains stationary. The torque applied to shaft 39 byslip clutch 29 makes one pair of disks, either 23 or 24, grip the belt25 tightly. Only if belt 25 is moving can the relative positions, of thetwo pairs of disks, 23,24 be changed.

Figure 2 diagrammatically depicts'a modified form of mechanism forcontrolling the variable speed transmission Here there is a governorgenerally indicated by 1 20 which controls the current to an electricmotor '44 which changes the speed of the transmission.

Governor 120 consists of a rotatable shaft 121 to which is fixedconnector 122 and on which is slidably mounted fiange123. Arms 124 arepivotally mounted to connector 122, and links125 connectarms 124 withflange 123. When flange 123 rises, a circuit is completed from Wire 51to wire 54 through contact 126, wire 51 being connected to the metallicgovernor as at 127. Shaft 121 is operatively connected to shaft 36 ofpump 35 by means of sprockets 13%, 131, and chain 132. a

. As previously described, when beam 12 unwinds, shafts 20, 21, shaft 35and pump 35 tend to increase in speed; Since shaft 121 of governor 120is operatively connected to shaft 36, the governor will also increaseits speed of rotation. As .the speed increases, arms 124 are thrownoutward by centrifugal force, and flange 123 rises to complete a circuitthrough contact 126. This closes the electrical circuit and current issupplied to motor-44 through wires 50 and 51. To reset the mechanismafter a beam has been unwound, reversing switch 53 and hand wheel 56 areused as described for Figure l.

Motor 44 could; be controlled by other electrical switches responsive tochanges in speed, such as a centrifugal switcher the speed responsiveswitch shown by the Butterworth et al. Patent N0. 2,392,226;

In the mechanisms described above, the braking mecha nismhasconsisted'or a. gear pump, whose braking force is determined-by theamount of press maintained in the discharge line.

. this gear pump could be replaced byct'her mechanical it will. ofcourse be understood that equivalents. a

fl-Having shown anddescribed preferred embodiments of the presentinvention, by way of examplerit should be the usual first shaft, secondshaft, andspeed changing,

mechanism, said-first shaft being arranged for engage. ment'with sa dbeam,'a gear pump, said second shaftbeing arranged for direct engagementwith saidgear pump, a

' reversible electric; motor including an electrical circuit thereto,said speed changing mechanism being arranged for engagement with saidreversible electric motor, and means for controlling said electricalcircuit by said gear pump.

2. in a constant web tension unwinding mechanism, a beam carrying theweb, said web travelling at a constant linear speed, a variable speedtransmission comprising the usual first shaft, second shaft and speedcontrolling shaft,

' reversible electric motor comprising an electric 'circuit,. 7

said first shaft being arranged for engagement withsaid beam, a gearpump comprising a reservoir, a discharge 7 line and a suction line, athrottling valve located in said discharge line, a Bourdon tubeconnected to said discharge line, said second shaft being arranged fordirect drive engagement with said" gear pump, 'a. reversible electricmotor including an electrical circuit thereto, said speed controllingshaft having a slip clutch which is arranged for engagement with saidreversible electric motor, a.

switch, in said electrical circuit for controlling the direction ofrotation of said reversible electric motor and 'a trolling saidelectrical circuit. I

3. in aconstant web tension unwinding mechanism, a beam carrying theweb, the web travelling at aconstant control switch forming part of saidBourdon tube for con linear velocity, a variable speed transmissioncomprising the two usual power transmitting shafts and speed changingmechanism, a driving connection between one of said shafts and saidbeam, a gear pump, comprising a reservoir, a discharge line and 'asuction line, a throttling valve locatedin'said discharge line, apressure responsive electrical switch in the'discharge line, a directdriving connection between the second of said shafts and said gear pump,a reversible electric motor, a source of electric current, said electricmotor being arranged. for engagement with said speed changing mechanism,said pressure responsive switch in circuit with said source and saidmotor. I

4. In a constant web tension unwindingmechanism, a

cam carrying the web, the web travelling at a constant linear velocity,avariable speed transmission comprising the two usual powertransmittingshafts and speed changing mechanism, a driving connectionbetween one' of said shafts and said beam, a gear pump comprising areservoir, 7

a discharge line and a suction line, a throttling valve lo cated in saiddischarge line, a pressure responsive electric switch in the dischargeline, a direct driving connection between the second of said shafts andsaid gear pump, a

reversible electric motor, a source of electric current, said electricmotor being arranged for engagement with said speed changing mechanism,said pressure responsive switch in circuit with said source andsaidmotor.

5. in a constant web tension unwinding mechanism, a beam carrying theweb, said web travelling at a constant linear speed, a variable speedtransmission provided with 'a first shaft, a second shaft, and speedchanging mechanism, said first shaft being arranged for engagement withsaid beam, a gear pump-, said second shaft being arranged for directengagement with said gear pump, a

said speed changing mechanism being arranged for engagement with saidreversible'electric motor, and means responsiveto thespeed of rotationof said gear pump for controlling said electric circuit. 1

6. in a constant web tension unwindingmech-anism, a beam carrying'a web,said web travelling at a constant linear speed, a variable speedtransmission provided with i a first shaft, a second shaft and speedchanging mechanism, I

said first shaft being arranged for engagement with said earn, a gearpump, said second shaft being arranged for direct engagement with saidgear pump, a reversible elec-- tric motor including an electric circuitthereto, said speed changing mechanism being arranged for engagementwith Y said-reversible electric-motor, and means'forr-controlling saidelectriccircuit by said gear pump, said means including a normally openelectric switch in said electric circuit. a I V 7.1m a constant webtension unwinding mechanism according to claim 6 wherein the engagementarrangement between said speed changing mechanism and said electricmotor includes a slip clutch.

8. In a constant Web tension unwinding mechanism according to claim 6wherein a pressure gauge and a throttling valve are positioned in thedischarge line of said pump.

9. In a constant web tension unwinding mechanism according to claim 6wherein a governor is connected to said gear pump and operates to closethe said normally open electric switch.

References Cited in the file of this patent UNITED STATES PATENTS

